Optical imaging is useful in a variety of contexts to produce a desired optical effect. The imaging may produce an image that is the same size as the object or it may involve magnification or reduction in the size of the image relative to the object being imaged. In addition, the image may be reversed or rotated about a vertical axis relative to the object and/or the image may be flipped or rotated about a horizontal axis relative to the object. Furthermore, the image may be reproduced sharply or it may appear slightly diffused relative to the object.
In another aspect, optical imaging may involve the production of an image in a different location from the object being imaged. One example of that type of imaging is in the use of an overhead projector to provide an image on a screen or wall based on an object located on a platform of the overhead projector. This type of imaging is typically accomplished with the use of lenses and other optical components.
In still another aspect, optical imaging occurs in retroreflection where an image of an object is produced at the same location as the object. Retroreflection occurs when incident light rays are reflected from an article along a path that forms a 180 degree angle with the path followed by the light when approaching the article. Depending on the nature of the article, the reflected path of the light may be shifted or offset slightly from the incident path of the light. Because the light is returned along substantially the same path it traveled towards the imaging article, the image can be viewed along that same path. Retroreflection is typically accomplished using retroreflective components such as cube corners (e.g., U.S. Pat. No. 5,272,562 to Coderre and U.S. Pat. No. 5,450,235 to Smith et al.), beaded retroreflectors (e.g., U.S. Pat. No. 4,025,159 to McGrath; U.S. Pat. No. 4,983,436 to Bailey et al.; and U.S. Pat. No. 5,066,098 to Kult et al.), etc.
In both of the above aspects of imaging, the need for optical components such as lenses, cube comer articles, beaded retroreflectors, etc. increases the cost and/or complexity of the imaging articles.